Some electronic circuits generate an unusually large amount of heat such as those circuits that are used in power supplies. Metal-backed circuit boards are frequently used in such applications, and are often designed for surface-mounted components and direct chip-attached components. Normally these cards are cooled by air convection, frequently by forced air directed across the surface of the circuit board. However, as the need to further miniaturize power supplies and other unusually high heat-generating applications becomes a significant design issue, cards which are cooled by air convection become unsatisfactory. Hot spots under components may be generated and either the size of the metal-backed printed circuit board must increase for better heat dissipation or the life of the components will decrease.
To solve the above-stated problem, the inventors herein have incorporated a flat heat pipe directly into the copper layer of the metal-backed card, thereby eliminating hot spots and enabling the delivery of significantly more power by a given card because of increased cooling capacity. Additionally, longer component life is provided by maintaining all components at approximately the same temperature. Smaller form factor cards are made possible through the improved cooling arrangement. These improvements are accomplished by incorporating a heat pipe at the copper layer thereby eliminating thermal contact resistance between the circuit board and the heat pipe as compared to previous arrangements where heat pipes are attached to cards in an external manner.
Japanese patent application 286395 relates to the use of small heat pipes located between two "prepregs" with a printed board located on the opposite side of the prepreg from the heat pipes. Thus, a laminated assembly is provided with heat pipes ensconced within the prepregs and not directly connected to the circuit board itself.
U.S. Pat. No. 4,727,455 relates to a semi-conductor power module with an integrated heat pipe. Semi-conductor power components are located in openings formed in a ceramic carrier plate. Heat pipes are integrated into the structure between the ceramic carrier plate and a ceramic baseplate.
U.S. Pat. No. 4,327,399 relates to a cooling arrangement for integrated circuit chips in which a heat pipe structure is located within the ceramic or silicon substrate.
Japanese patent application 54-78670 also relates to a ceramic heat pipe incorporated into the substrate of components.